\Sour\, v. t. [AS. s?rian to sour, to become sour.]
1. To cause to become sour; to cause to turn from sweet to
sour; as, exposure to the air sours many substances.
So the sun's heat, with different powers, Ripens the
grape, the liquor sours. --Swift.
2. To make cold and unproductive, as soil. --Mortimer.
3. To make unhappy, uneasy, or less agreeable.
To sour your happiness I must report, The queen is
dead. --Shak.
4. To cause or permit to become harsh or unkindly. ``Souring
his cheeks.'' --Shak.
Pride had not sour'd nor wrath debased my heart.
--Harte.
5. To macerate, and render fit for plaster or mortar; as, to
sour lime for business purposes.

\Sour\, v. i. [imp. & p. p. {Soured}; p. pr. & vb. n.
{Souring}.]
To become sour; to turn from sweet to sour; as, milk soon
sours in hot weather; a kind temper sometimes sours in
adversity.
They keep out melancholy from the virtuous, and hinder
the hatred of vice from souring into severity.
--Addison.